It is well known that cardiac arrhythmias may be controlled with devices such as implantable defibrillators. Previous endocardial lead electrodes used with such devices are disclosed in Mirowski et al., U.S. Pat. No. 3,942,536 and Kinney et al., U.S. Pat. No. 4,161,952, and epicardial electrodes are disclosed in Heilman et al., U.S. Pat. No. 4,030,509 and Heilman et al., U.S. Pat. No. 4,291,707.
In U.S. Pat. No. 5,016,808 to Heil, Jr. et al., an implantable endocardial defibrillation lead is suggested wherein a conductive deposited electrode is produced by plating or vapor deposition of a conductive material onto a tubular body.
Endocardial lead electrodes have several functional requirements which must be met. Firstly, the electrodes must be able to deliver large amounts of electrical current. Secondly, it is desirable that the electrodes have large surface areas so that the energy can be delivered over a large area of the heart and the current can be evenly distributed. In so doing, current density is decreased and the chance of damaging heart tissues is significantly lessened. Thirdly, the electrodes must be flexible and fatigue resistant to provide ease of implantation and avoid lead fracture.
Because of their location within the heart, electrodes must endure constant motion and millions of flex cycles.
Past implantable electrodes have been made with materials such as titanium that are biocompatible. However, these biocompatible materials may be deficient in other areas such as anodic corrosion resistance, current carrying capability or mechanical fatigue properties.
Accordingly, there is a need for an improved implantable defibrillation electrode that is able to deliver large amounts of current over large surface areas. In addition there is a need for a defibrillation electrode that allows the current to be evenly distributed. There is also a need for a defibrillation electrode that has improved fatigue resistance over previously known electrodes. The present invention satisfies the above-identified needs.